People don’t like to be wrong. When you have published a slew of papers, books, given public talks, taught a couple of generations of students to be told it was all wrong is hard to take. It’s the sunk cost fallacy us humans are very prone to. Us scientists are humans with careers and reputations and too often that trumps the science.
But the data will continue to come. They tried to get dna from the bones and layers but failed. But there will be a cave out there in the Americas with pre Clovis dna in it I’’m sure.
Considering Australia was reached 50-60kya the much later date for the Americas is curious. We know people made dugout canoes, maybe lashed them together to make catamaran paddled rafts. That gets you around the coasts in Beringia and you follow it down until there’s enough ice free land you can walk inland.
There may have been founder effects with genetic isolation. We’re a very inbred species to start with. Doesn’t take long for the recessive genes to start to come out. Maybe they died out, maybe Clovis supplanted them with better tech. Or maybe the disease burden of Clovis did for them.
Trading up the Amazon killed the great jungle civilisations when Europeans were only on the coasts. By the time Europeans got into the interior the jungle had grown over the cities. It took Lidar and ground penetrating radar to reveal the cities and the remains of the field systems.
Obsidian which can be fingerprinted to individual volcanoes has been used to prove long range inter island trade in the Pacific. For several generations after settlement the people of Aotearoa were trading with the homeland (Tahitii, Mangareva, Tuamotus). Us humans will trade.